Events By Place Europe July 20 - Rollo besieged Chartres. Autumn — Charles the Simple agrees to the Treaty of St.-Claire-sur-Epte, ceding the lower Seine area to the Norse and Norman invaders under Rollo, the first Duke of Normandy. The town of Drogheda, Ireland's founded by the Danes. Prince Oleg of Novgorod raids the Byzantine Empire and forces Leo VI the Wise to sign a trade agreement. By Topic Religion April — Pope Anastasius III succeeds Pope Sergius III as the 120th pop… (More on 911)